At the present cosmic epoch, only the most massive galaxies appear to have ceased active star formation. For the remainder, sustaining star formation requires an adequate supply of interstellar gas, and it is far from clear where this gas comes from. While there is enough gas in the intergalactic medium to provide a continuing fuel supply, it is unlikely to fall onto the centres of galaxies where star formation is expected to be quenched most rapidly. Nor does infall of intergalactic gas naturally explain the pattern of star formation seen in dwarf galaxies, which have extraordinarily large gas fractions. In this talk I argue that, by combining novel mechanisms for regulating star formation with an understanding of how gas is transported through galaxies, we can understand the pattern of which galaxies form stars at what rates, and where within those galaxies star formation takes place.